Eccentric mass actuator for power hammer



Sept. 29, 1964 A. H. OELKERS ECCENTRIC MASS ACTUATOR FOR POWER HAMMER Filed April 1, 1963 2 Sheets-Sheet l ATTORNE VJ p 29, 1964 A. H. OELKERS 3,150,724

ECCENTRIC MASS ACTUATOR FOR POWER HAMMER Filed April 1, 1963 2 Sheets-Sheet 2 l hL/O M Huh.

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United States Patent 3,150,724 ECCENTRIC MASS ACTUATOR FOR POWER HAMMER Alfred H. Oelkers, 424 Normandy, San Antonio, Tex. Filed Apr. 1, 1963, Ser. No. 269,555 Claims. (Cl. 17349) This invention relates to improvements in power hammers for delivering a succession of heavy impacts.

Hammers of this general type are commonly used in the construction and repair of roadways, as, for example, in the tamping of loose soil and the breaking up of old pavement. They may comprise double-acting drop hammers, jack hammers and various heavy weight dropping devices, all of which are of complicated construction and susceptible of frequent malfunction because they require complex hydraulically or pneumatically operated mechanisms for reciprocating the impact element.

An object of this invention is to provide a power hammer which does not require complex mechanisms of the type above mentioned and may, in fact, be operated simply by means of a conventional power take-off drive shaft on a vehicle or other power source.

Another object is to provide such a power hammer which is especially well suited for use on a mobile support, whereby it may be moved over a roadbed to be worked, in that its impact element may be extended over the end of the support without causing appreciable unbalance of the cover-all weight of the support.

Still another object is to provide such a power hammer which may be operated and repaired by unskilled personnel, and which is easily and quickly adjustable insofar as the amount and type of work to be performed is concerned.

A further object is to provide such a power hammer which is compact and inexpensive in construction and whose operating mechanisms are not subject to large amounts of shock due to impact.

These and other objects are accomplished in accordance with the illustrated embodiments of this invention, by a power hammer including a support, which may be vehicular or otherwise mobile, and an arm pivotally mounted on the support at one end and extending substantially horizontally therefrom. A hammer head is mounted on the free-swinging end of the arm for oscillating therewith in an arcuate path about the axis of its pivotal mounting and above the surface to be hammered, which, in the case of a mobile supported arm, may be beyond the end of the support.

The arm and thus the hammer head is caused to so oscillate by means of weights connected to the arm intermediate its ends for rotation about axes parallel to the axis of the pivotal mounting, together with means for rotating the weights in opposite directions and at the same speed. More particularly, these weights, each of which is mounted eccentrically on an axle fixed to the arm, are equal in size and spacing from their respective axes of rotation so as to have equal moments of inertia thereabout and are so arranged as to exert oppositely directed centrifugal forces on the hammer arm which are of maximum value when at least substantially parallel to the path of oscillation of the hammer head and at least substantially balanced in directions perpendicular to this path. Thus, at impact, the hammer head will deliver maximum force in a direction perpendicular to the arm as well as the surface being hammered. Also, since the centrifugal forces are balanced in the manner described, they place no burdens on the shaft which would require oversized bearings.

The only power required to operate the hammer is that necessary to rotate the weights and this may be derived 3,15%,724- Patented Sept. 29, 1964 from a power take-off shaft on the vehicle when the arm is supported on same. Furthermore, with the hammer supported upon a vehicle, as is contemplated in a preferred embodiment of the invention, the rotating weights may be disposed at most any desired location intermediate the ends thereof so as to counterbalance the weight of the hammer head on the outer, free-swinging end of the arm.

The energy of the hammer is adjustable by a change in any one or more of the size of the weights, spacing of the weights from the axes about which they rotate, and the speed at which they rotate. This not only gives the power hammer wide flexibility, but also enables it to be adjusted by unskilled personnel. Still further, and in a preferred embodiment of the invention, the hammer head is mounted on a separate pivotally mounted arm which is resiliently connected to the arm to which the weights are connected, so as to cushion the impact of the blows transmitted to the mechanism for rotating the weights.

In the drawings, wherein like reference characters are used throughout to designate like parts:

FIG. 1 is a side elevational view of a power hammer constructed in accordance with one embodiment of the present invention and supported upon a vehicle for movement over a pavement which is to be broken up, with the arm, head, and weights of the hammer being shown in solid lines at the point of impact with the pavement and in broken lines at the point of maximum upward travel either prior to or following the impact;

FIG. 2 is a top plan view of the power hammer of FIG. 1;

FIG. 3 is an enlarged sectional view of the power hammer of FIGS. 1 and 2, as seen along broken line 3-3 of FIG. 2, and illustrating the resilient connection of the hammer arm to the power arm;

FIG. 4 is a side elevational view of another embodiment of power hammer constructed in accordance with the present invention; and

FIG. 5 is a top plan view of the power hammer shown in FIG. 4.

With reference now to the details of the above-described drawings, and particularly FIGS. 1 to 3, the power hammer shown therein, and designated in its entirety by reference character 10, comprises a vehicle 11 having a frame 12 supported upon wheels 13 movable over a surface 14, which in this illustrated case comprises a pavement which is to be broken up. This vehicle may be propelled in any suitable manner, as by a gasoline engine including a main drive shaft 15 connecting through transmission 16 with a power take-off shaft 17. Obviously, the transmission may be of a variable speed type so that the power take-off shaft 17 may be rotated at a number of desired speeds for any given speed of rotation of the drive shaft 15;

The power hammer also includes an arm 18 which is pivotally mounted at one end upon a shaft 19 journaled within bearing portions 20 on the forward portion of the frame 12 of the vehicle and extending horizontally therefrom to a rear portion of the vehicle. As will be described more fully hereinafter, weights 21 connected to the arm 18 intermediate its opposite ends are of such size and so arranged that, when rotated in opposite directions about an axis parallel to the axis of shaft 19, they exert oppositely directed centrifugal forces on the arm so as to oscillate the arm 18 in an arcuate path indicated in FIG. 1'. The hammer also includes another arm 22 which is also pivotally mounted about the shaft 19 and extends rearwardly of the vehicle substantially parallel to the arm 18. The outer free-swinging end of the arm 22 extends beyond the end of the arm 18 and carries a means 23 for mounting a hammer head 24 above a surface to the rear of the vehicle, so that when arm 22 is connected to arm 18, the head 24 will also oscillate in the path shown.

Thus, as illustrated in FIG. 1, the impact of the oscillating hammer head 24 will break the pavement at a location just rearwardly of the vehicle, so that the vehicle may be moved progressively forwardly in the direction of the work to be performed. In the active position of the hammer head shown in solid lines, the arms 18 and 22 are disposed substantially parallel to the surface 14. When the hammer is not in use, the lower end of the head 24 may be raised above the surface 14 by means of a cable 25 connected between an outer portion 26 of the hammer arm and a winch 27 which may be powered by means of the vehicle. As can be seen from FIG. 1, an intermediate portion of the cable is guided over a sheave 28 supported from an A-frame 29 on the frame of the vehicle.

As best shown in FIG. 2, the arm 18 comprises spaced sides 18a and 1812 connected at their inner ends by a cross member 180. The hammer arm 22 also comprises side members 22a and 22b which are disposed outboard of the sides of the arm 18, but inboard of the bearing portions 20 of the frame of the vehicle. The outer ends of the side members 18a and 18b are connected by a rectangular frame 18a, and there is an intermediate cross member 30 extending between the sides 22a and 22b of the hammer arm and having a forwardly extending flange 31 thereon disposed between the upper and lower portions of the rectangular frame 18d on the power arm. As also shown in FIG. 3, a series of coil springs 31a or resilient members are disposed between the rectangular frame and the upper and lower sides of flange 31 so as to thereby cushion the impact of the hammer head 24 which is transmitted to the mechanism (to be described) connecting the weights 21 with the means for rotating same.

As shown in FIGS. 1 and 2, the hammer head mounting means 23 comprises a laterally extending member 32 connecting the outer ends of sides 22a and 22b and having an opening therethrough to receive the upper end of head 24. Although the details of this mounting are unimportant, it will be noted that this permits the hammer head 24 to be replaced with another of any desired configuration depending on the work to be done.

The weights 21 are rotatable about an axle 33 (see FIG. 1) fixed to and extending between the sides 18a and 18b of the power arm. Preferably, the axle is so mounted toward the outer end of such arm, but not far from the center of gravity of the vehicle. A pair of identical sprockets 34 are mounted upon the axle 33 each for rotation in a direction opposite to that of the other sprocket, but in a plane parallel thereto. More particularly, each such sprocket carries a flange 34a to which a weight 21 is removably connected by means of bolts 34b or the like.

More particularly, the flanges 34a are disposed on the inner sides of the sprockets 34 so that the planes in which the weights 21 rotate are relatively close together. As can be seen from FIG. 1, these weights are of equal size and spaced equally from the axis of axle 33 so that they have equal moments of inertia with respect to such axis. Thus, it will be understood that when these weights are diametrically opposed to one another during rotation in opposite directions, in a manner to be described hereinafter, they will simultaneously exert equal and oppositely directed centrifugal forces. On the other hand, when these weights pass one another during such rotation, they will exert a centrifugal force on the axle and thus on each of the power arm and hammer arm which is the sum of the centrifugal force of each.

As shown in FIGS. 1 and 2, shaft 19 is rotated by the power take-off shaft 17 through a belt 35 disposed about pulleys 36 and 37 on the shafts. As shown in FIG. 2, a sprocket 38 is fixed to the shaft 19 for rotation therewith and is connected by means of a chain 39 to one of 4- the sprockets 34. A gear 40, which is also connected to the shaft 19 for rotation therewith, is drivingly engaged with a gear 41 of the same size and mounted upon a shaft 42 extending between the sides 18a and 18b of the power arm 18. More particularly, the gear 41 is keyed or otherwise secured to the shaft 42 so as to rotate it at the same speed as the shaft 19. A sprocket 43 of the same size as the sprocket 38 is keyed to the shaft 42 for rotation with it and connected by means of a chain 44 to the other sprocket 34 on the axle 33. In this way, the two gears 34 upon which the weights 21 are carried will not only rotate in opposite directions, but also at the same speed.

As will be apparent from FIG. 1, the weights 21 are so arranged on the sprockets 34 that they will pass one another at intervals perpendicularly above and below the arm 18 to which they are connected. At these times of passing each other their centrifugal forces will be in the same direction thereby alternately exerting combined upward and downward pulls on arm 18 and thus upon hammer head 24. At the same time, and as also previously described, the centrifugal forces exerted by the rotating weights in directions perpendicular to the path of oscillation of the hammer head, and thus in line with the arms 18 and 22, will be at least substantially balanced.

The resilient connection of the hammer arm to the power arm will, as previously noted, relieve the abovedescribed drive mechanism between the shaft 19 and the weights 21 of substantially all of the impact of the hammer head. Thus, a greater proportion of this impact will be transmitted directly through the hammer arm 22 to the shaft 19, and the sprockets, gears and chains making up the drive connection will except a longer life free of damage.

As shown in FIG. 1, the weights 21 will have passed one another and be on the upwardly moving portion of their cycle at the time of impact of the hammer head 24. That is, the hammer head will lag somewhat behind the downwardly directed centrifugal force of the weights, the amount of the lag depending upon the speed of rotation of the weights. This, of course, is beneficial to the operation of the power hammer since it eliminates a good deal of the jarring effect on the weights which would otherwise occur if the impact came at the instant the weights were reaching their lowermost position. Conversely, at the time the hammer head is raised to its uppermost position, the weights will have passed one another and be moving downwardly, as shown in broken lines in FIG. 1.

It is known that the force due to a mass revolving about a stationary axis is directly proportional to the weight of the mass and the square of the linear velocity of the mass and inversely proportional to the radial distance of the mass from the axis. Presumably, the formula for the force of such a mass when it revolves about an oscillating axis, as in the present invention, is a function of the same factors. Thus, the amount of force produced by this power hammer may be adjusted in any number of ways, as by changing the speed of rotation, size and/or radial spacing of the weights.

Although the speed of rotation of the weights, and thus the frequency of the hammer blows is directly proportional to the speed of rotation of the shaft 19, the linear speed of the weights may be altered by shortening or lengthening their radial spacing from their axis of rotation. Since the weights are readily removable from the flanges 34a, they may be replaced by weights of different sizes. Furthermore, since the weights in the embodiment of FIGS. 1 to 3 rotate in spaced-apart planes, the operator is given a wide selection.

Of course, the weights must be rotated at a speed which is suflicient to raise the hammer head upwardly after it has been forced downwardly to deliver a blow. The energy driving the mechanismi.e., rotating the weights, oscillating the arms and hammer head-is converted to L: kinetic energy until the instant of impact. This kinetic energy is partly absorbed by the work done, partly rebounded, and partly absorbed by friction.

With reference now to the details of FIGS. 4 and 5, the power hammer shown therein, and designated in its entirety by reference character 45, also includes an arm 46 pivotally mounted upon a shaft 47 carried by a support 48. As in the power hammer shown and described in connection with FIGS. 1 to 3, the support 48 may be a vehicle or other means movable over the surface of the ground in connection with roadway work. Alternatively, of course, the support may comprise a pair of trunnions mounted in a stationary position. In any case, however, the arm 46 extends horizontally therefrom to its outer free-swinging end which carries a means 49 for supporting a hammer head 50. However, as distinguished from the previously described embodiment of the invention, this hammer head is connected directly to the power arm 46. For this reason, it is preferred that coil springs 51 or other shock absorbing means be disposed between the mounting means 49 and the upper and lower enlargements 52 and 53 on the hammer head.

Similarly to the power hammer of FIGS. 1 to 3, weights 54 are connected to the power arm 46 intermediate the shaft 47 and hammer head mounting means 49 each for rotation about an axis parallel to the axis of shaft 47. More particularly, the weights are mounted upong cars 55 and 56 which rotate in opposite directions about axles 57 and 58, respectively, carried by the arm 46. However, in the power hammer 45, the axles 57 and 58 are spaced along the arm and the gears 55 and 56 engage one another so as to rotate the weights in opposite directions and about longitudinally spaced-apart axes. More particularly, the arm 46 comprises spaced sides 46a. and 461), which are pivotally connected about the shaft 47 inboard of the supports 48 and connected at their outer ends by the transversely extending hammer head mounting means 49. The axles 57 and 58 are fixed to and extend between the sides so as to support the gears as well as the weights within them.

As can be seen from FIGS. 4 and 5, the gears 57 and 58 are of equal size so that they will turn at the same speed as they are rotated in engagement with one another. Also, as in the case of the weights described in connection with the embodiment of FIGS. 1 to 3, the weights 54 are of the same size and equally spaced from the axes of axles 57 and 58 so that they have equalmoments of inertia thereabout. As can also be seen from FIGS. 4 and 5, the weights are carried on the same sides of the gears so that they rotate in substantially the same plane.

The shaft 47 is rotated by means of a suitable power source including a rotatable shaft 59, the shafts being connected by a belt 60 disposed about pulleys 47a and 59a keyed to them. When the support 48 comprises a vehicle, for example, the shaft 59 may comprise a suitable power take-off, as in the case of the shaft 17 previously described. At any rate, the rotation of shaft 47 is transmitted to the gear 55 and thus to the gear 56 by means of a chain 61 disposed about a sprocket 62 keyed to the shaft 47 and a sprocket 63 keyed to the axle 57.

As best shown in FIG. 5, the drive connections between the weights 54 and the shaft 47 are also disposed between the sides 46a and 46b of the arm 46. As in the case of the previously described embodiment of the invention, the weights 54 are so arranged as to exert oppositely directed centrifugal forces on the arm 46 which are of maximum value when at least substantially parallel to the path of oscillation of the hammer head about the axis of shaft 47. Still further, the centrifugal forces caused by rotation of the weights 54 are at least substantially balanced in directions perpendicular to this path of oscillation or lengthwise of the arm 46 so that there is a minimum of strain upon the bearings between the shaft and the arm 46. As in the case of the weights 21 previously described, the weights 54 are removable so that they may be replaced by weights of other sizes as well as weights adapted to have their moments of inertia spaced at different radial distances from the axes of the axles 57 and 58.

It will also be obvious to those skilled in the art that, although, in its preferred form, the power hammer of the present invention has a vehicular support so that it may be moved over a roadway, other uses of the power hammer are contemplated, both upon a stationary or a mobile support. For example, this hammer may be used in the crushing of ores and rocks, in the kneading of clay, rubber or other relatively soft material, etc.

From the foregoing it will be seen that this invention is one well adapted to attain all of the ends and objects hereinabove set forth, together with other advantages which are obvious and which are inherent to the apparatus.

It will be understood that certain features and subcombinations are of utility and may be employed without reference to other features and subcombinations. This is contemplated by and is within the scope of the claims.

As many possible embodiments may be made of the invention Without departing from the scope thereof, it is to be understood that all matter herein set forth or shown in the accompanying drawings is to be interpreted as illustrative and not in a limiting sense.

The invention having been described, what is claimed 1. A power hammer, comprising a vehicular support, an arm having one end pivotally mounted on the support and the opposite end extending beyond said support, means for mounting a hammer head on the opposite freeswinging end of the arm for oscillation therewith in an arcuate path about the axis of the pivotal mounting, and means connected to the arm intermediate its opposite ends for so oscillating the hammer head, including weights each [of which is rotatable about an axis parallel to the axis of the pivotal mounting, and means for rotating the weights in opposite directions and at the same speed for exerting oppositely directed centrifugal forces on said arm which are of maximum value when at least substantially parallel to the path of oscillation of the hammer head and which are at least substantially balanced in directions perpendicular to said path.

2. A power hammer, comprising a mobile support, an arm having one end pivotally mounted on the support, a hammer head on the opposite end of the arm for freely oscillating therewith in an arcuate path about the axis of the pivotal mounting, and means for so oscillating the hammer head, including weights each of which is mounted on the arm for rotation about an axis parallel to the axis of the pivotal mounting, and means for rotating the weights in opposite directions and at the same speed so as to exert oppositely directed centrifugal forces on the arm which are of maximum value when at least substantially parallel to the path of oscillation of the hammer head and which are at least substantially balanced in directions perpendicular to said path.

3. A power hammer, comprising a support, an arm pivotally mounted at one end to the support and having means on its opposite end to mount a hammer head for free oscillation therewith in an arcuate path about the axis of the pivotal mounting, and means for so oscillating the hammer head in said arcuate path, including weights mounted eccentrically on at least one axle on the arm each for rotation about an axis parallel to the axis of the pivotal mounting, and means for rotating the weights in opposite directions and at the same speed to cause them to exert oppositely directed centrifugal forces on said arm which are of maximum value When at least substantially parallel to the path of oscillation of the hammer head and which are at least substantially balanced in directions perpendicular to said path.

4. A power hammer of the character defined in claim 3,

wherein all of the weights are mounted on a single axle for rotation about a common axis.

5. A power hammer of the character defined in claim 3, wherein there are a pair of axles spaced longitudinally along the length of the arm so that the weights rotate about longitudinally spaced-apart axes.

6. A power hammer, comprising a support having a shaft, means for rotating the shaft, an arm pivotally mounted at one end on the shaft, means on the opposite free-swinging end of the arm for mounting a hammer head for oscillation therewith in an arcuate path about the axis of the shaft, weights mounted on the arm intermediate its opposite ends each for rotation about an axis parallel to the axis of the shaft, and drive connections between the shaft rotating means and the weights for rotating the weights in opposite directions and at the same speed to cause them to so oscillate the hammer head by exerting oppositely directed centrifugal forces on said arm which are of a maximum value when at least substantially parallel to the path of oscillation of the hammer arm and which are at least substantially balanced in directions perpendicular to said path.

7. A power hammer, comprising a support, an arm having one end pivotally mounted on the support, means on the opposite end of the arm to mount a hammer head for freely oscillating therewith in an arcuate path about the axis of the pivotal mounting of said arm, another arm having one end pivotally mounted on the support and having a resilient connection with the hammer arm toward the free-swinging end of said hammer arm, weights mounted on the other arm each for rotation about an axis parallel to the axis of the pivotal mounting of said other arm, and means for rotating the Weights in opposite directions and at the same speed to cause them to oscillate the other arm and thereby so oscillate the hammer arm and head by exerting oppositely directed centrifugal forces on said other arm which are of maximum value when at least substantially parallel to the path of oscillation of the hammer head and which are at least substantially balanced in directions perpendicular to said path.

8. A power hammer of the character defined in claim 7, wherein the support includes a rotatable shaft and both arms are pivotally mounted on said shaft, said weight rotating means including drive connections between each weight and the shaft, and means for rotating the shaft.

9. A power hammer, comprising a support having a rotatable shaft, means for rotating the shaft, an arm having one end pivotally mounted on the shaft, axles mounted on the arm toward its opposite end and spaced from one another longitudinally of the arm, sprockets mounted on the axles for rotation about axes parallel to the axis of the shaft and connected to one another for rotation in opposite directions and at the same speed, means connecting the shaft with one of the sprockets for rotating both said sprockets, means for mounting a hammer on the free end of the arm, and equal weights mounted on the sprockets with their moments of inertia at equal distances from the axes of rotation of the sprockets and so arranged relative to one another as to exert oppositely directed centrifugal forces on the arm which are of maximum value when at least substantially parallel to the path of oscillation of the hammer head and which are at least substantially balanced in directions perpendicular to said path.

10. A power hammer, comprising a support having a rotatable shaft, means for rotating the shaft, an arm having one end pivotally mounted on the shaft, an axle mounted on the arm toward its opposite end, a pair of sprockets mounted on the axle for rotation about a common axis parallel to the axis of the shaft, means connecting each of the sprockets to the shaft for rotating them in opposite directions and at the same speed, means for mounting a hammer on the free end of the arm, and equal weights mounted on the sprockets with their m0- ments of inertia at equal distances from the axis of rotation of sprockets and so arranged relative to one another as to exert oppositely directed centrifugal forces on the arm which are of maximum value when at least substantially parallel to the path of oscillation of the hammer head and which are at least substantially balanced in directions perpendicular to said path.

References Cited in the file of this patent UNITED STATES PATENTS 

2. A POWER HAMMER, COMPRISING A MOBILE SUPPORT, AN ARM HAVING ONE END PIVOTALLY MOUNTED ON THE SUPPORT, A HAMMER HEAD ON THE OPPOSITE END OF THE ARM FOR FREELY OSCILLATING THEREWITH IN AN ARCUATE PATH ABOUT THE AXIS OF THE PIVOTAL MOUNTING, AND MEANS FOR SO OSCILLATING THE HAMMER HEAD, INCLUDING WEIGHTS EACH OF WHICH IS MOUNTED ON THE ARM FOR ROTATION ABOUT AN AXIS PARALLEL TO THE AXIS OF THE PIVOTAL MOUNTING, AND MEANS FOR ROTATING THE WEIGHTS IN OPPOSITE DIRECTIONS AND AT THE SAME SPEED SO AS TO EXERT OPPOSITELY DIRECTED CENTRIFUGAL FORCES ON THE ARM WHICH ARE OF MAXIMUM VALUE WHEN AT LEAST SUBSTANTIALLY PARALLEL TO THE PATH OF OSCILLATION OF THE HAMMER HEAD AND WHICH ARE AT LEAST SUBSTANTIALLY BALANCED IN DIRECTIONS PERPENDICULAR TO SAID PATH. 